BOX issues Area Forecast Discussion (AFD) at Sep 2, 8:02 AM EDT249
FXUS61 KBOX 021202
AFDBOX
Area Forecast Discussion
National Weather Service Boston/Norton MA
802 AM EDT Wed Sep 2 2026
.WHAT HAS CHANGED...
No major changes to the forecast with this update.&&
.KEY MESSAGES...
- Cloudy and drier today with an increasing chance of showers and
thunderstorms late tonight into Thursday morning.
- Rain continues Thursday with a chance for a strong thunderstorm or
two during the afternoon.
- Mix of clouds and sun with diurnally driven spot showers
Friday into the early part of Labor Day Weekend, but drier
weather most of the time. Dry and seasonable Sunday and on the
Monday holiday, with onshore breezes.
&&
.KEY MESSAGES...
- Cloudy and drier today with an increasing chance of showers and
thunderstorms late tonight into Thursday morning.
- Rain continues Thursday with a chance for a strong thunderstorm or
two during the afternoon.
- Mix of clouds and sun with diurnally driven spot showers
Friday into the early part of Labor Day Weekend, but drier
weather most of the time. Dry and seasonable Sunday and on the
Monday holiday, with onshore breezes.
&&
.DISCUSSION...
KEY MESSAGE 1...Cloudy and drier today with an increasing chance of
showers and thunderstorms late tonight into Thursday morning.
Expecting a mainly dry but cloudy day today as a 1026 mb surface
high builds over the Canadian Maritimes and extends SE toward s
southern New England. Cloud cover will keep high temperatures in the
upper 60s to low 70s for most locations. Onshore flow means that
coastal areas likely see the coolest temps while the warmest
conditions will be found across the interior. The day ends on an
unsettled note as a frontal wave approaches from the Great Lakes. At
the surface, a warm front approaches southern New England overnight
bringing the return of a moisture-rich airmass to the region.
Precipitable water values rise to 1-1.8" overnight. Lift provided by
the jet positioned to the west and warm front will support the
return of showers and perhaps some embedded, mostly elevated storms.
Showers/storms more likely arrive in west and central portions of
southern New England 11 PM to 2 AM arriving in the I-95 corridor 4
AM- 7 AM. There are indications of marginal elevated instability
that accompanies the plume of richer moisture. While instability
looks to be marginal (MLCAPE 400-700 J/kg), a strengthening low
level jet on the order of 35-45 kts helps to increase the low-level
wind field. Thus, any storms that form to the west of our CWA likely
continue as they head east despite lower instability levels.
Steering flow appears strong enough to support quicker storm motion
which would limit the risk for flash flooding. If there are embedded
storms and downpours, can't rule out the potential for poor
drainage/urban flooding in the more vulnerable spots. As a result,
there is a marginal (level 1 of 4) risk for excessive rainfall and
localized flash flooding.
KEY MESSAGE 2...Rain continues Thursday with a chance for a strong
thunderstorm or two during the afternoon.
Yet another shortwave impulse dives S from eastern Canada Thursday.
An associated surface cold front provides lift for showers and
thunderstorms by the afternoon The main question mark is on if
storms could become strong in this timeframe. Although the airmass
is plenty humid and mid and upper level wind fields are seasonably
strong, considerable cloud cover could temper how much
destabilization occurs. GFS-based CAPE profiles show about 800-1600
J/kg of most-unstable CAPE with moist-adiabatic mid-level lapse
rates also tempering instability. It's still debatable if storms
could become strong but the chances seem low with more tempered
instability favored. Still, Thursday looks to be a washout with
good chances for rains during the daytime hours, with more
substantial clearing taking place Thursday evening.
KEY MESSAGE 3...Mix of clouds and sun with diurnally driven spot
showers Friday into the early part of Labor Day Weekend, but drier
weather most of the time. Dry and seasonable Sunday and on the
Monday holiday, with onshore breezes.
Still under cyclonic flow aloft for Friday into the early part of
Labor Day Weekend. This will keep weather pattern somewhat unsettled
with a mix of clouds and sun. Spot showers are possible Friday and
Saturday afternoon but drier weather prevails most of the time. much
of the time. Broad high pressure then works in from the north Sunday
into Labor Day, leading to onshore breezes, but with partly sunny
skies and dry conditions.
&&
.AVIATION /12Z WEDNESDAY THROUGH SUNDAY/...
Forecaster Confidence Levels...
Low - less than 30 percent.
Moderate - 30 to 60 percent.
High - greater than 60 percent.
12z TAF Update:
Today...High confidence.
Patchy MVFR this morning improving to VFR by 15Z. Mid-level
clouds remain throughout the day. Winds ENE this morning
becoming ESE in the afternoon at 6-12 kts, turning SSW around
and after 00Z.
Tonight...High confidence in trends, moderate confidence in
timing -SHRA/CIGS
Showers arrive overnight with embedded thunder possible from
west to east between 02Z and 08Z. Lower ceilings accompany the
showers/few storms falling to MVFR/IFR. SSE winds 5-10 kts.
Thursday...High confidence in trends.
MVFR/IFR to start with -SHRA and a few embedded storms exiting
12-15Z. Winds turn to SSW in that timeframe at 6-10 kts. Expect
improvements toward VFR 15Z into mid-afternoon. MVFR ceilings
may linger for Cape/Islands through around 00Z.
KBOS Terminal...High confidence in TAF. MVFR ceilings this
morning, likely trending to VFR by 15Z. Showers arrive
overnight, likely arriving by 06Z accompanied by MVFR
ceilings/vsbys, potentially IFR. Few embedded heavier showers or
rumble thunder possible, but too low prob to put in TAF.
KBDL Terminal...High confidence in TAF. MVFR ceilings this
morning becoming VFR by afternoon. Showers arrive by around 04Z
with a few embedded heavier SHRA/embedded storms possible.
Probabilities too low to include in TAF at this time.
Outlook /Thursday through Sunday/...
Wednesday Night: Mainly VFR, with areas IFR possible. SHRA
likely, isolated TSRA.
Thursday: Mainly VFR, with local IFR possible. Breezy. Chance
SHRA, slight chance TSRA, patchy BR.
Thursday Night through Friday Night: VFR.
Saturday: VFR. Breezy. Chance SHRA.
Saturday Night through Sunday: VFR. Breezy.
&&
.MARINE...
Forecaster Confidence Levels...
Low - less than 30 percent.
Moderate - 30 to 60 percent.
High - greater than 60 percent.
Through Tonight...High confidence.
SCA gusts (~25 kts) continue through 12z this morning for the
southern waters tonight with seas 3-5 ft. A SCA is in effect for
the southern waters through sunrise this morning. Marginal to
near SCA conditions continue through much of the day today with
E winds between 15 and 20 kts and seas between 2 and 4 feet.
Conditions eventually relax overnight ahead of low pressure
approaching from the west.
Outlook /Thursday through Sunday/...
Wednesday Night: Winds less than 25 kt. Areas of seas
approaching 5 ft. Chance of rain showers, isolated
thunderstorms.
Thursday: Winds less than 25 kt. Chance of rain showers, slight
chance of thunderstorms, patchy fog.
Thursday Night: Winds less than 25 kt. Chance of rain showers,
slight chance of thunderstorms.
Friday through Friday Night: Winds less than 25 kt.
Saturday: Low risk for Small Craft Advisory winds with gusts up
to 25 kt. Areas of seas approaching 5 ft.
Saturday Night through Sunday: Low risk for Small Craft
Advisory winds with gusts up to 25 kt. Seas up to 5 ft.
&&
.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...None.
RI...None.
MARINE...Small Craft Advisory until 8 AM EDT this morning for ANZ235-
237-255-256.
&&
$$
DISCUSSION...Loconto/FT
AVIATION...Mensch/FT
MARINE...Loconto/Mensch/FT
Source:
BOX issues Area Forecast Discussion (AFD) at Sep 2, 8:02 AM EDT----------------
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